The pressure drop predictions across a bypass pipeline in dense phase pneumatic conveying were investigated numerically. The simulation was conducted using the commercial Computational Fluid Dynamic (CFD) software Fluent with the Euler- Euler model accounting for four-way coupling. Experiments and calculations were conducted using flyash powder conveyed in a horizontal pipeline. The influence of the pipe length on pressure drop prediction was also investigated. The results indicate that pressure prediction of the CFD simulation model for a bypass pipe is promising. The conclusion is that this investigation can offer improved insight and initial design modelling capability for bypass pneumatic conveying systems.